The present invention relates to a microscope that is protected against thermal expansion due to heat from an illumination optical system.
During observation under a microscope, an observer takes a comfortable position, with his or her arms placed on a desk or takes notes on a desk. In light of this, a microscope is designed such that its base is narrow to make as large as possible the remaining area of a desk on which the microscope is placed.
Because of this, many recent microscopes contain a power supply for turning on a lamp at their back, as shown in FIGS. 1 and 2.
In a transmitted-light type microscope in FIG. 1, an arm 3 is provided in U-shaped formation through a frame 2 on a base 1. A stage 5 is slidably installed on the frame 2 to mount a specimen 4. An objective lens 7 is attached through a revolver 6 to the arm 3. The microscope also has an observation optical system 8. A lamp housing 11 with a lamp 9 and a collector lens 10 which are intended to give transmitted illumination to the specimen 4 is disposed on the base 1. The frame 2 contains a power supply 12 for turning on the lamp 9.
In a reflected-light type microscope in FIG. 2, on the other hand, a reflected-light optical system 13 and the lamp housing 11 are provided on the arm 3. The frame 2 also contains the power supply 12 for turning on the lamp 9.
When a specimen is observed under such a microscope as shown in FIG. 1 or FIG. 2, heat generated from the lamp 9 is conducted to the base 1 and the frame 2, thereby expanding the microscope, so that the distance between the stage 5 bearing the specimen 4 and the objective lens 7 changes by a few micrometers. This change greatly affects the excessively narrow focal depth range of the microscope, resulting in undesirable movement of an already adjusted focal point.
Illuminating observation using a microscope is roughly classified into two types, i.e., an observation under transmitted illumination and an observation under reflected illumination. For the observation under transmitted-illumination, a lens tube is attached directly to the arm, or an intermediate lens tube, such as a magnification changer or an imager, is provided between the arm and the lens tube.
For the observation under reflected illumination, a reflected-light floodlight tube, containing a reflected-light optical system, is attached to the arm. In this case, the reflected-light floodlight tube must have not only an optical system but also sufficient space to allow a polarizing plate needed for polarization observation to be removable. Accordingly, a reflected-light floodlight tube is more spacious in the direction of the optical axis than an intermediate tube, such as a magnification changer or an imager. For optical performance reasons, the distance between the objective-lens and the lens tube is limited. A thicker microscope arm is more rigid. However, because making the microscope arm thicker affects the thickness of the reflected-light floodlight tube, it is not feasible to excessively thicken a microscope arm.
According to Jpn. Pat. Appln. KOKAI Publication No. 9-120030, a focal point shift in the direction of the optical axis due to thermal expansion of a microscope is reduced by disposing two rods combined together which differ in coefficient of thermal expansion between the rack and stage of the microscope so that the rods expand due to heat in opposite directions.
According to Jpn. Pat. Appln. KOKAI Publication No. 10-142508, a reflected-light floodlight tube is installed near the border between the frame and arm of a microscope, and a fastening member is provided on top of the frame to increase the rigidity of the arm.
According to Jpn. UM Appln. KOKOKU Publication No. 55-24566, a thin arm with a replaceable arm, which assembly is equivalent to a conventional microscope attachment, is integrated with the arm to make the end of the arm stronger.
According to Jpn. Pat. Appln. KOKAI Publication No. 9-120030 also, the rack and stage are connected together through the two rods. However, the stage is considerably fragile because of a long distance between the rack and stage. Accordingly, if a load or a force is applied to the stage, the image of a specimen greatly moves.
According to Jpn. Pat. Appln. KOKAI Publication No. 10-142508, a microscope using a large intermediate lens tube, such as a reflected-light floodlight tube, is made more rigid. Because the thickness of the arm is limited so that if no intermediate lens tube is used, optical performance is attained which is required when an intermediate lens tube is incorporated, the arm disclosed in the publication is thin and poorly rigid. More lens tubes have been used in combination with an intermediate lens tube, with a heavy television camera placed on them. In such uses, a poorly rigid arm poses a problem.
According to Jpn. UM Appln. KOKOKU Publication No. 55-24566, an arm connection is of a dovetail type. The dovetailed connection is short and unsuitable for an arm which undergoes a large moment. The connection is not resistant to a force parallel to the dovetailed contact surface.
Jpn. Pat. Appln. KOKAI Publication No. 10-142508 and Jpn. UM Appln. KOKOKU Publication No. 55-24566 disclose no corrective action against thermal deformation. What is worse, according to these publications, the thickness of an observable specimen is limited; that is, only a specimen with a thickness equivalent to the travel of a stage can be observed.
As described below, in a microscope with a power supply incorporated at the back of the microscope body, thermal expansion of a metal plate securing the power supply adversely affects the microscope body, so that the focal point shifts.
FIG. 4 shows the structure of a microscope with a power supply and a metal plate incorporated at the back of the microscope body.
A base 100 has a support 101 and an arm 102 combined together. In the rear of the base 100, a lamp housing 103 is provided, in which a lamp 104 and a collector lens 105 are installed to illuminate a specimen 4. A diffusing plate 106, a field stop 107, and a mirror 108 are provided in the base 100, which is in the optical path for illumination light emitted from the lamp housing 103. A window lens 109 is disposed in the optical path through which illumination light reflected upward at the mirror 108 passes. The window lens 109 concentrates illumination light on the specimen 4.
The support 101 has a stage guide 110 which can move up and down. The stage guide 110, which mounts the specimen 4, is lifted or lowered by turning an aiming handle 111, installed on the base 100. That is, the aiming handle 111 is connected with a pinion gear 112, which is engaged with a planetary gear 113. Because the planetary gear 113 is engaged with a rack 114 installed on the stage guide 110, using screws, rotation of the aiming handle 111 is transmitted from the pinion gear 112 through the planetary gear 113 to the rack 114, thereby moving the stage guide 110 up and down.
At its bottom, the arm 102 is fitted with an objective lens 116 through a revolver 115. A lens tube 117 is installed on top of the arm 102.
The support 101 contains a power supply 118 for turning on the lamp 104.
In a microscope incorporating such a power supply 118 at its back (support 101), the power supply 118 is secured to come in extensive contact with a metal plate 119, that is, a good conductor of heat, thereby absorbing and dissipating heat generated from the power supply 118, and the metal plate is secured to the support 101 of the microscope body, using a plurality of fasteners, such as screws, as shown in FIG. 5, a top view of the microscope, and FIG. 6, a rear view thereof. To shut off electrical noise from the power supply 118, the metal plate 119 is desirably made of metal.
Heat generated from the power supply 118 causes the temperature of the metal plate 119 to rise, so that the plate expands due to heat. Accordingly, deformation occurs due to heat from the metal plate 119, as shown by the arrow in FIG. 6. The deformation adversely affects the microscope body, thereby moving an adjusted focal point.
Jpn. Registered Design Publication No. 922010 discloses a Y type microscope intended to increase the remaining area of a desk on which the microscope is placed. In the microscope, the power supply is secured to a W-shaped metal plate 121 so that the power supply comes in extensive contact with the plate, and the metal plate 121 is fastened to the back of the W-shaped microscope body, using a plurality of fastening members, e.g., screws 123, as shown in FIG. 7.
However, it is difficult to tap the microscope body and install the screws in the same direction to fasten the metal plate 121 to the back of the Y type microscope body, using the plurality of screws 123. Moreover, the number of machining and assembly steps increases, resulting in a higher manufacturing cost.